feat(proto): add protocol primitives

proto/src/message/primitive/pgstring.rs

@@ -0,0 +1,54 @@
+use bincode::de::Decoder;
+use bincode::enc::write::Writer;
+use bincode::enc::Encoder;
+use bincode::error::{DecodeError, EncodeError};
+use bincode::{BorrowDecode, Decode, Encode};
+
+#[derive(Debug, Clone, BorrowDecode)]
+pub struct PgString(String);
+
+impl PgString {
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+}
+
+impl From<&str> for PgString {
+    fn from(string: &str) -> Self {
+        PgString(string.to_string())
+    }
+}
+
+impl From<PgString> for String {
+    fn from(pg_string: PgString) -> Self {
+        pg_string.0
+    }
+}
+
+impl From<String> for PgString {
+    fn from(string: String) -> Self {
+        PgString(string)
+    }
+}
+
+impl Encode for PgString {
+    fn encode<E: Encoder>(&self, encoder: &mut E) -> Result<(), EncodeError> {
+        encoder.writer().write(self.0.as_bytes())?;
+        encoder.writer().write(b"\0")
+    }
+}
+
+impl Decode for PgString {
+    fn decode<D: Decoder>(decoder: &mut D) -> Result<Self, DecodeError> {
+        let mut string = String::new();
+        loop {
+            let byte = u8::decode(decoder)?;
+            if byte == 0 {
+                break;
+            }
+            string.push(byte as char);
+        }
+
+        Ok(PgString(string))
+    }
+}